Coater and method for producing coated sgeet and air floating mini-turn bar

ABSTRACT

In an apparatus for applying a film of coating solution to each side of a web such as paper, resin film, etc., there is provided an air-flotation type mini turn bar ( 4 ) to the downstream side of the nipping portions ( 20 ) of two applicator rolls ( 2,2 ). The air-flotation type mini turn bar ( 4 ) is used to convey the web ( 1 ) while holding the web on the surface of one of the two applicator rolls ( 2 ), after it passes between the nipping portions ( 20 ). In this way, the occurrence of flaws in the coated surfaces of the web ( 1 ) is prevented, the occurrence of a mist and coating unevenness is suppressed, and a film of coating solution is formed evenly on each side of the web.

TECHNICAL FIELD

The present invention relates to an apparatus and method, which are usedin paper-making machines, resin-film manufacturing machines, etc., forapplying a coating solution to the surface of a web such as paper, resinfilm, etc., and also relates to an air-flotation type mini turn bar thatis suitably used in the coating apparatus.

BACKGROUND ART

In paper-making machines, resin-film manufacturing machines, etc., thereis provided an apparatus for applying a coating solution to the surfaceof a web such as paper, resin film, etc.

FIG. 14 is a simplified side view showing a conventional coatingapparatus. As illustrated in the figure, a web 1, such as paper, etc.,is fed from a previous step and passes between the web-nipping portions20 of two applicator rolls 2 which are formed when they are pressedagainst each other. After the web 1 is coated with a coating solution,it goes into a drier 6 via a turn bar (air-flotation/non-contact typeweb-travel supporting unit) 5 that conveys the web 1 while floating it.

The application of a coating solution to both sides of the web 1 isperformed as follows:

Each applicator roll 2 includes a main body 2 a made of metal such assteel, etc. The roll main body 2 a has an elastic film 2 b such as afilm of rubber on the outer periphery. Each applicator roll 2 rotates atthe same circumferential speed as the travel speed of the web 1. Theapplicator roll 2 is equipped with a coater head 3, which is a means ofsupplying a coating solution to the surface of the elastic film 2 b.

The coater head 3 contains measurement means such as a coating solutionsupply passage, measuring rod, blade, etc. After a sufficient quantityof coating solution is supplied from the coater head 3 to the surface ofthe applicator roll 2, at the exist of the coater head the measuring rodis pressed against the surface of the applicator roll 2 to form a filmof coating solution with a predetermined thickness on the surface of theapplicator roll 2.

Note that the film thickness of the coating solution on the applicatorroll 2 is adjusted by controlling the force of pressing the measuringrod or blade against the applicator roll 2. The technique of forming afilm of coating solution on the applicator roll 2, described above, iswell known in the prior art (see, for example, Y. Miura, “Trend of theLatest Coater-Size Press Technique,” Paper-Pulp Technique Times, No. 12,1997) and is not particularly limited.

A film of coating solution formed on each of the applicator rolls 2 bythe above-described technique is transferred and applied to each side ofthe web 1 as it passes between the web-nipping portions 20 of theapplicator rolls 2 which are formed when they are pressed against eachother.

The web 1 with a film of coating solution transferred and applied toeach side is conveyed to a drier 6. At this time, as shown in FIG. 14,if the coating solution, transferred and applied from the applicatorrolls 2 to the web 1, is in an undried state and contacts a solid objectsuch as a conveyance roll during conveyance, the coated surface will beflawed and the quality will be considerably degraded. Because of this,in the web conveyance between the web-nipping portions 20 of theapplicator rolls 2 and drier 6, there is used an air floater, or a turnbar 5 called a non-contact type guide member.

The non-contact type guide member 5 is used to support and convey theweb 1 without contacting the web surface by floating the web 1 with theforce of air. Therefore, the web 1 can be conveyed to the drier 6without degrading the quality of the coated surface in an undried state,formed on the surface of the web 1.

Now, a description will be given of problems found in theabove-described conventional technique.

In the case where the web 1 is paper that absorbs water, waterabsorption sometimes causes elongation and shrinkage of the web 1, if acoating solution is transferred and applied to the web 1. Also, in thecase where the web 1 is resin film, etc., and is elongated or shrunk bythe temperature of a coating solution, elongation and shrinkagesometimes occurs in the web 1, if a film of coating solution istransferred and applied to each side of the web 1 at the web-nippingportions 20 of the applicator rolls 2.

On the other hand, the above-described conventional technique, as shownin FIG. 14, does not have any device that regulates the path of the web1 between the web-nipping portions 20 of the applicator rolls 2 and theturn bar 5.

Therefore, in the case where there occurs elongation and shrinkage inthe web 1, and the web 1 is elongated particularly at the exist of theweb-nipping portions 20, the web 1 sometimes travels while sticking tothe surface of one of the upper and lower applicator rolls 2 because ofthe stickiness of a coating solution, as shown in FIG. 15.

When the web 1 is wide (in the width direction of the applicator roll2), the state of sticking becomes uneven in the width direction of theweb 1. That is, one portion of the web 1 in the web width directionsticks to the upper applicator roll 2, while another portion sticks tothe lower applicator roll 2. Therefore, there are cases where the web 1vibrates between the surfaces of the upper and lower applicator rolls 2.

In the case where coating operations are performed at high speeds, thereare cases where the state of uneven sticking starts to fluctuatetemporally and becomes unstable. This phenomenon is disclosed, forexample, in Japanese Laid-Open Patent Publication No. HEI 7-163924.

When the position and angle at which the web 1 is separated from theapplicator roll 2 are uneven and unstable, there are cases where coatingunevenness, called peeling patterns such as that shown by referencenumeral 11 in FIG. 16, take places in the coated film on the web 1. Thisphenomenon is, for example, the same as that shown in FIGS. 4 and 8 ofJapanese Patent No. 2578183.

The above-described phenomenon is considered to take place for thefollowing reasons: when the coating solution between the surface of theweb 1 and the surface of the applicator roll 2 is split between theapplicator roll side and the web surface side after the web 1 passesbetween the web-nipping portions of the applicator rolls 2, the meniscusof the split solution becomes unstable; as a result, the transfer rateof the coating solution that is transferred from the applicator roll 2to the web surface becomes temporally and spatially unstable; and thefilm thickness of the coating solution formed on the web surface becomesuneven.

In addition to the peeling patterns, there is a fear of a mistingphenomenon occurring. That is, in the case of high-speed coatingoperations, a coating solution scatters in drops because of theabove-described meniscus unstableness. If this phenomenon takes place,the coating apparatus and coated paper will be stained with a coatingsolution and there will be a possibility of operations being suspended.

The present invention has been made in view of the circumstancesdescribed above. Accordingly, it is the object of the present inventionto provide a coating apparatus and coating method which are capable ofevenly forming a film of coating solution on each side of a web bysuppressing the occurrence of a mist and coating unevenness, whilepreventing the occurrence of flaws in the coated surfaces.

DISCLOSURE OF THE INVENTION

To achieve this end, there is provided an apparatus that transfers andapplies a film of coating solution on each of two applicator rolls toeach side of a web as it passes between web-nipping portions of the twoapplicator rolls which are formed when they are pressed against eachother. The apparatus includes an air-flotation type mini turn bar, whichis provided to the downstream side of the web-nipping portions. Theair-flotation type mini turn bar is used to convey the web while holdingthe web on the surface of one of the two applicator rolls, after the webpasses between the web-nipping portions.

According to the coating apparatus of the present invention, theair-flotation type mini turn bar is able to convey the web while holdingthe web on the surface of one of the two applicator rolls, after the webpasses between the web-nipping portions. By forcibly holding the web onthe surface of one of the two applicator rolls, the position at whichthe web is separated from the applicator roll becomes stable. Forinstance, the occurrence of coating unevenness called peeling patternscan be prevented, and consequently, coating quality can be considerablyenhanced.

Preferably, the coating apparatus of the present invention furtherincludes a mechanism that moves the mini turn bar. Preferably, themini-turn-bar moving mechanism is constructed to adjust the distancethat the wed is held on one of the two applicator rolls, or adjust thedistance between the one applicator roll and the mini turn bar. Byproviding the mini-turn-bar moving mechanism, the separation of the webfrom one of the two applicator rolls and the application of a coatingsolution from the one applicator roll to the web can be adjusted.

Preferably, the coating apparatus of the present invention furtherincludes a paper roll, which is provided to the upstream side of theweb-nipping portions. The paper roll is used to convey the web whileholding the web on the surface of the other of the two applicator rolls,before the web passes between the web-nipping portions. By providing thepaper roll, the application of a coating solution from the otherapplicator roll to the web can be suitably adjusted.

In this case, the coating apparatus of the present invention preferablyincludes a mechanism that moves the paper roll. By providing thepaper-roll moving mechanism (position adjustment mechanism), theapplication of a coating solution from the other applicator roll to theweb can be suitably adjusted.

In accordance with the present invention, there is provided anair-flotation type mini turn bar that causes a web to travel so as toform an arcuately curved portion around the bar by floating the web withair. The air-flotation type mini turn bar includes a first air pocketarranged inside the arcuately curved portion of the web; a second airpocket provided adjacent to the first air pocket and arranged near anentrance portion of the curved portion; a third air pocket providedadjacent to the first air pocket and arranged near an exit portion ofthe curved portion; a first air nozzle provided between the first airpocket and the second air pocket for squirting air toward the web; and asecond air nozzle provided between the first air pocket and the thirdair pocket for squirting air toward the web.

According to the above-described air-flotation type mini turn bar, thebottom surface of the curved portion of the web can be stably supportedby both the dynamic pressure of air squired from each of the air nozzlesand the static pressure of air within each of the air pockets, and theweb is able to travel so as to form an arcuately curved portion aroundthe mini turn bar without being contacted by the mini turn bar.Therefore, in the case where the web is coated paper, there is nopossibility that the coated surfaces of the web will contact the miniturn bar, and the problem of flaws in coated surfaces can be prevented.

Preferably, the air-flotation type mini turn bar further includes athird air nozzle that squirts higher-pressure air than atmosphericpressure into the first air pocket. According to the third air nozzle,the static pressure within the first air pocket is made higher. This cancompensate for a reduction in the dynamic pressure component of the wakeair in the partition wall portion between air pockets, particularly thefirst air pocket and third air pocket. Therefore, the web and partitionwall portion can be prevented from contacting each other because ofnegative pressure.

Preferably, a shape from the second air pocket to the third air pocketis formed symmetrically with respect to the center line of the first airpocket. According to this shape, the web can travel along a path havinga fixed radius of curvature and stable web travel becomes possible.

Furthermore, the air-flotation type mini turn bar preferably adopts alabyrinth structure. That is, the air-flotation type mini turn barfurther includes a plurality of first baffle walls, which are providedin the direction of the width of the web within the first air pocket sothat the first air pocket is segmented into a plurality of sections.Also, the air-flotation type mini turn bar includes a plurality ofsecond baffle walls and a plurality of third baffle walls. The secondbaffle walls are provided in the direction of the width of the webwithin the second air pocket so that the second air pocket is segmentedinto a plurality of sections. The third baffle walls are provided in thedirection of the width of the web within the third air pocket so thatthe third air pocket is segmented into a plurality of sections.According to this labyrinth structure, the web can be supported by thestatic pressure within each section. Therefore, even when the web shiftsin the width direction, a fluctuation in the supporting pressure isslight. Also, since each baffle wall is resistant to the wake air, theinterior static pressure becomes higher. Therefore, according to such alabyrinth structure, the web can be more stably supported and the webcan be prevented from vibrating and making a noise.

Preferably, the second air nozzle includes a second air-jet surface anda second slit-shaped air-jet groove, which are provided on a thirdsurface extending in the direction of the width of the web. The secondair-jet surface has a great number of air-jet bores and is provided nearthe first air pocket. The second air-jet groove extends in the directionof the width of the web and is provided near the third air pocket.

The structure of the second air nozzle can reliably prevent contact ofthe web at the baffle wall portion between the first air pocket andthird air pocket where contact with the web is liable to occur becauseof a reduction in the dynamic pressure component of the wake air.Preferably, the first air nozzle has the same structure as the secondair nozzle. That is, the first air nozzle includes a first air-jetsurface and a first slit-shaped air-jet groove, which are provided onthe third surface extending in the direction of the width of the web.The first air-jet surface has a great number of air-jet bores and isprovided near the first air pocket. The first air-jet groove extends inthe direction of the width of the web and is provided near the secondair pocket.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be described in further detail with referenceto the accompanying drawings wherein:

FIG. 1 is a simplified side view showing a coating apparatus constructedin accordance with a first embodiment of the present invention;

FIG. 2 is a simplified side view showing a mini turn bar constructed inaccordance with the first embodiment of the present invention;

FIG. 3A is a simplified sectional view showing an example of the miniturn bar of the first embodiment;

FIG. 3B is a simplified sectional view showing another example of themini turn bar of the first embodiment;

FIG. 4 is a simplified side view showing a coating apparatus constructedin accordance with a second embodiment of the present invention;

FIG. 5 is a simplified side view showing a coating apparatus constructedin accordance with a third embodiment of the present invention;

FIG. 6 is a simplified side view showing an alteration of the coatingapparatus constructed in accordance with the third embodiment of thepresent invention;

FIG. 7 is a simplified sectional view showing a first mini turn bar thatis preferable in structure to the mini turn bar of the first embodiment;

FIG. 8 is a simplified sectional view showing a second mini turn barthat is preferable in structure to the mini turn bar of the firstembodiment;

FIG. 9 is a simplified sectional view showing a third mini turn bar thatis preferable in structure to the mini turn bar of the first embodiment;

FIG. 10 is a simplified sectional view showing a fourth mini turn barthat is preferable in structure to the mini turn bar of the firstembodiment;

FIG. 11 is a simplified sectional view showing a fifth mini turn barthat is preferable in structure to the mini turn bar of the firstembodiment;

FIG. 12A is a simplified sectional view showing a sixth mini turn barthat is preferable in structure to the mini turn bar of the firstembodiment;

FIG. 12B is a plan view of the mini turn bar seen from A direction ofFIG. 12A and denotes the baffle plate by hatching for distinction;

FIG. 13 is a simplified sectional view showing a seventh mini turn barthat is preferable in structure to the mini turn bar of the firstembodiment;

FIG. 14 is a simplified side view showing a conventional coatingapparatus;

FIG. 15 is a simplified side view of web-nipping portions used toexplain problems found in the conventional coating apparatus; and

FIG. 16 is a simplified plan view of a web used to explain problemsfound in the conventional coating apparatus.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will hereinafter be described withreference to the drawings.

(A) First Embodiment

First, a first embodiment of the present invention will be described inconjunction with the drawings.

As illustrated in FIG. 1, a coating apparatus is equipped with twoapplicator rolls 2, 2, which are arranged opposite each other so as toform web-nipping portions 20 when they are pressed against each other. Afilm of coating solution, supplied to each of the applicator rolls 2,2by a coater head 3, is transferred and applied to each side of a web 1as it passes between the web-nipping portions 20. The coated web 1 isguided without being contacted by a turn bar (air-flotation/non-contacttype web-travel supporting unit) 5 and goes into a drier 6. Eachapplicator roll 2, as with the above-described conventional applicatorroll, includes a main body 2 a made of metal such as steel, etc. Theroll main body 2 a has an elastic film 2 b such as a film of rubber onthe outer periphery.

The coating apparatus, as illustrated in FIGS. 1 and 2, further includesan air-flotation type mini turn bar 4 (which is anair-flotation/non-contact type web-travel support unit and smaller insize than the turn bar 5, and which will hereinafter be referred tosimply as a mini turn bar). The mini turn bar 4 functions as aweb-separating unit and is arranged in close proximity to a portion ofone of the two applicator rolls 2 (e.g., the upper applicator roll 2 inthe first embodiment) which is downstream from the web-nipping portion20. The mini turn bar 4 is used to convey the web 1 while holding it onthe surface of the upper applicator roll 2. In this way, the position atwhich the web 1 with a film of coating solution is separated from theupper applicator roll 2 is stabilized, and the web-separating positionis kept constant in the direction of the width of the web 1.

This mini turn bar 4 has, for example, a cross section such as thatshown in FIGS. 2 and 3A and extends in the width direction of the web 1.The mini turn bar 4 is equipped with an internal space (flow passageway)4 a to which compressed air is supplied, a guide surface 4 b disposedopposite the web 1, and nozzles 4 c, 4 d provided in the guide surface 4b. The nozzles 4 c, 4 d are used to squirt the compressed air within theinterior space 4 a toward the web 1.

With this arrangement, the mini turn bar 4 presses the web 1 toward thesurface of the upper applicator roll 2 without contacting the web 1 bythe compressed air squirted from the nozzles 4 c, 4 d. That is, the pathof the web 1 is directed toward the upper applicator roll side by themini turn bar 4.

As a result, the web 1 contacts the surface of the upper applicator roll2 a little longer, but since the angle α at which the web 1 is separatedfrom the upper applicator roll 2 becomes greater, the position at whichthe web is separated becomes stable.

That is, as shown in FIGS. 1 and 2, by arranging the mini turn bar 4,the web 1 from the web-nipping portions 20 of the applicator rolls 2travels while it is being held on the surface of the upper applicatorroll 2. And at the position of the mini turn bar 4, the web 1 isforcibly separated toward the position of the turn bar 5. At this time,the mini turn bar 4 creates a layer of air between the web 1 and theguide surface 4 b of the mini turn bar 4. Since this layer of airprevents the surface of the coated web 1 from contacting the mini turnbar 4, degradation in the quality of the coated web 1 is prevented.

To create a layer of air between the guide surface 4 b of the mini turnbar 4 and the web 1, the guide surface 4 b facing the web 1 is providedwith nozzles 4 c, 4 d. Also, the surface 4 b facing the web 1 is formedas an air-jet guide surface that has a smoothly curved cross section.

The nozzles 4 c, 4 d are constructed as a great number of holesjuxtaposed in the longitudinal direction of the mini turn bar 4, or theyare constructed as two slits extending in the longitudinal direction, orthey are constructed as a combination of such holes and slits.

Also, in the first embodiment, the nozzles 4 c, 4 d are provided on thefront side (downstream side in the traveling direction of the web 1) andrear side (upstream in the traveling direction of the web 1) of theguide surface 4 b, respectively. The nozzles 4 c, 4 d are constructed tosquirt compressed air in the directions of arrows a1 and a2,respectively. This is for the purpose of creating a stable layer of airbetween the guide surface 4 b and the web 1 and stably causing the pathof the web 1 to be close to one of the two applicator rolls 2.

To stably cause the path of the web 1 to be close to one of the twoapplicator rolls 2, it is effective not only to squirt compressed airtoward the web 1, but also to create a stable layer of air between theweb guide surface 4 b and the web 1 so that air is stored between theweb guide surface 4 b and the web 1. If both nozzles 4 c, 4 d areactuated, air is stored between the guide surface 4 b and the web 1 anda stable layer of air can be created between the guide surface 4 b andthe web 1. Hence, the nozzles 4 c, 4 d are formed in the front and rearportions of the guide surface 4 b, respectively.

To effectively utilize the energy of the squirted air for floating theweb 1 off the guide surface 4 b, it is preferable that the air-jet angleθ of each of the nozzles 4 c, 4 d (i.e., the angle of the air-jetdirection relative to the reference surface 4 e of the mini turn bar 4)be within a predetermined range (e.g., a range of approximately 15 to 90degrees).

That is, if the air-jet angle θ becomes 90 degrees or greater, thegreater part of a flow of air from each of the nozzles 4 c, 4 d willflow out of the front and rear portions of the guide surface 4 b. As aresult, the force acting on the web 1 is greatly reduced, the force ofpressing the web 1 toward the upper applicator roll 2 becomes weak, andit becomes difficult to cause the web 1 to move along a predeterminedpath.

On the other hand, if the air-jet angle θ is too small (e.g., less than15 degrees), the force of pressing the web 1 toward one of the twoapplicator rolls 2 is similarly weakened, it becomes difficult to causethe web 1 to move along a predetermined path, and there is a possibilitythat the web 1 will come into contact with the mini turn bar 4.

Note that even if the air-jet force that acts on the web 1 is weak, itis possible to cause the web 1 to move along a predetermined path bylowering web tension. However, in this case, as shown by a two-dot chainline in FIG. 3A, the web 1 bulges out in the vicinity of the centralportion of the guide surface 4 b, and consequently, the web 1 cannottravel smoothly. Therefore, web tension cannot be lowered greatly, andif the air-jet force acting on the web 1 is weak, it is fairly difficultto cause the web 1 to move along a predetermined path.

Thus, it is preferable that the angle of the air-jet direction of eachof the nozzles 4 c, 4 d relative to the reference surface 4 e be withina predetermined range (e.g., a range of approximately 15 to 90 degrees).

Also, for the position at which the web 1 is separated from the surfaceof the upper applicator roll 2 to be stable and constant in the widthdirection of the web 1, it is preferable to set the radius R ofcurvature of the front surface (guide surface) 4 b of the mini turn bar4 within a predetermined range (e.g., a range of 20 to 400 mm). And itis also preferable to cause the web 1 to travel along a path curved soas to correspond to the radius R of curvature.

Note that an optimum value for the radius R of curvature of the guidesurface 4 b (which corresponds to the radius of the path of the web 1 atthe position of the guide surface 4 b) varies with the layout of a roll,drier, etc., and web tension. The optimum value also varies with theviscosity of a solution that is applied to the web 1 by the coater head3. For example, when the viscosity of a solution is low and there is noneed to separate the web 1 from the surface of the applicator roll 2abruptly, the radius R of curvature may be great. However, when theviscosity of a solution is high and the web 1 needs to be separated fromthe surface of the applicator roll 2 abruptly, the radius R of curvaturehas to be small.

In addition to the radius R of curvature of the guide surface 4 b, it ispreferable to optimally set the specification of the mini turn bar 4,such as the air-jet angle and air-jet strength of the nozzles 4 c and 4d, etc., in accordance with the viscosity of a solution to be applied tothe web 1, web tension, and layout of each element.

Note that there is a relation of P=T/R between the radius R ofcurvature, the tension T of the web 1, and the pressure P applied to theweb 1 by the nozzles 4 c, 4 d. The radius R of curvature, web tension T,and pressure P (air-jet angle θ and air-jet strength of the nozzles 4 c,4 d) are set so as to meet the above-described relation.

As shown in FIG. 3B, the guide surface 4 b of the mini turn bar 4 facingthe web 1 may be provided with a concave static pressure pocket 4 f. Byreliably holding a jet of air on the guide surface 4 b by the staticpressure pocket 4 f, the jet of air can be effectively utilized forfloating the web 1 off the mini turn bar 4. That is, the energy of airsquirted from the nozzles 4 c, 4 d can be effectively converted intopressure that presses the web 1 toward one of the two applicator rolls2.

Since the coating apparatus of the first embodiment of the presentinvention is constructed as described above, the application of acoating solution to the web 1 is performed in the following steps(method of applying a coating solution to the web 1, constructed inaccordance with the first embodiment).

That is, the web 1 is fed into the coating apparatus from a previousstep, and a coating solution is applied to each side of the web 1 at theweb-nipping portions of the upper and lower applicator rolls 2. At thistime, a film of coating solution is formed on each side of the web 1.The coated web 1 is conveyed to the turn bar 5 and drier 6.

In the coating apparatus and method of the first embodiment, the web 1first passes between the web-nipping portions 20. Then, the web 1travels while it is being held on the surface of one (upper) of the twoapplicator rolls 2 by a predetermined circumferential length by the miniturn bar 4. Next, the web 1 is forcibly separated from the upperapplicator roll 2 along the guide surface 4 b of the mini turn bar 4.

That is, by air squirted from the nozzles 4 c, 4 d of the mini turn bar4, the path of the web 1 from the web-nipping portions 20 toward theturn bar 5 is forcibly pushed toward the surface of one (upper) of thetwo applicator rolls 2 so that the web 1 is brought into contact withthe surface of the one applicator roll 2 for a long time and that theangle α at which the web 1 is separated from the surface of the oneapplicator roll 2 becomes great. Generally, if the angle α at which theweb 1 is separated is small, the web 1 is liable to vibrate at theposition where the web is separated (see FIG. 15), and therefore theposition at which the web 1 is separated becomes unstable. Conversely,if the angle α at which the web 1 is separated is great, the web 1 isless liable to vibrate and therefore the position at which the web 1 isseparated becomes stable.

Further, since the position at which the web 1 is separated becomesstable, a meniscus, which is formed as a film of coating solution issplit between the applicator roll side and the web surface side, becomesstable and the occurrence of a mist can be suppressed.

Thus, in the coating apparatus of the first embodiment, the separationangle α of the web 1 from the applicator roll 2 becomes greater by beingguided along the mini turn bar 4, the separation position of the web 1from the applicator roll 2 becomes stable and becomes constant in thewidth direction of the web 1, and the occurrence of a mist can besuppressed.

Hence, coating unevenness, called peeling patterns such as that shown inFIG. 16, and a mist, which are found in prior art, can be prevented fromoccurring in the coated film on the web 1.

Of course, because the mini turn bar 4 is of an air-flotation type,there is no possibility that the surface of the web 1 with a film ofcoating solution will make contact with the mini turn bar 4 and degradethe coating quality.

Thus, the occurrence of coating unevenness and a mist in the web 1 canbe prevented, while preventing the occurrence of a flaw in the coatedsurfaces of the web 1. Therefore, the formation of an even film ofcoating solution becomes possible and the coating quality and operatingenvironment are greatly enhanced.

Also, by setting the angle θ of the air-jet direction of each of thenozzles 4 c, 4 d within a predetermined range (e.g., a range ofapproximately 15 to 90 degrees), the energy of an air jet can beefficiently utilized for floating the web 1 off the guide surface 4 band there is no possibility that the web 1 will bulge out at the centralportion thereof (see the two-dot chain line in FIG. 3A). The path of theweb 1 is reliably altered by the mini turn bar 4, so the separationposition of the web 1 from the applicator roll 2 can be stabilized.

As shown in FIG. 3B, if the guide surface 4 b of the mini turn bar 4 isprovided with the static pressure pocket 4 f, the energy of a jet of aircan be more efficiently converted into pressure that floats the web 1off the guide surface 4 b. As a result, the flotation of the web 1 bythe mini turn bar 4 (toward one of two applicator rolls 2) can bereliably performed.

In the first embodiment, the contact (contact distance) of the web 1with one (upper) of the two applicator rolls 2 becomes longer, socoating conditions for both sides of the web 1 will differ. Because ofthis, as shown by reference numeral 1′ and a two-dot chain line in FIG.1, the angle at which the web 1 enters between the web-nipping portions20 can be adjusted so that the contact of the web 1 with the other(lower) applicator roll 2 becomes longer. In this way, coatingconditions for both sides of the web 1, particularly the capillaryosmotic conditions of a coating solution into the web 1 (base paper) canbe made equal. Also, the quantities of a coating solution that areapplied to both sides of the web 1 can be balanced as the coatingconditions required for each side of the web 1. In this case, thecoating apparatus may further include a guide roll (paper roll) 7, whichis arranged to the upstream side of the web-nipping portions 20 toadjust the angle at which the web 1 enters between the web-nippingportions 20.

Note that by permeating a coating solution into the web 1 while holdingit on the surface of the applicator roll 2, as described above, thethickness of the coating solution in the meniscus is reduced. At thesame time, a rise in the concentration of the coating solution in themeniscus loses the fluidity of the meniscus, so the meniscus breaks upin its early stages and the advantage of reducing the occurrence of amist is also obtained.

(B) Second Embodiment

Now, a second embodiment of the present invention will be described inconjunction with the drawings.

FIG. 4 shows a simplified side view of a coating apparatus constructedin accordance with the second embodiment of the present invention. Inthe figure, the same reference numerals as FIG. 1 denote the same partsand a description of these parts will be partly omitted.

As illustrated in FIG. 4, the coating apparatus of the second embodimenthas the same mini turn bar 4 as the first embodiment to the downstreamside of web-nipping portions 20. The coating apparatus further has thesame guide roll (paper roll) 7 as the alteration of the first embodiment(see the two-dot chain line in FIG. 1) to the upstream side of theweb-nipping portions 20.

In the second embodiment, the mini turn bar 4 is arranged so that theweb 1 is wound around a lower applicator roll 2. The paper roll 7 isarranged so that the web 1 is wound around an upper applicator roll 2.However, the mini turn bar 4 and paper roll 7 may be arranged in reverseorder with respect to the upper and lower applicator rolls 2,2.

In the second embodiment, a drier 6 and turn bar 5 are arranged to thedownstream side of the applicator rolls 2,2 in the reverse order of thefirst embodiment. However, they are arranged properly in accordance withdevice-installation environment, etc.

And in the second embodiment, the mini turn bar 4 and paper roll 7 areprovided with moving mechanisms (not shown), respectively. Becausevarious moving mechanisms are well known in the prior art, a descriptionof the detailed structures will not be given.

The mini-turn-bar moving mechanism is used to properly move the miniturn bar 4 in a direction away from or toward the applicator roll 2 orcircumferential direction of the applicator roll 2 or combined directionof these directions (e.g., a direction from the position of referencenumeral 4′ in FIG. 4 to the position of reference numeral 4). By movingthe mini turn bar 4 in that direction, the contact length that the web 1contacts one (lower) of the two applicator rolls 2 (i.e., the distancethat the web 1 is held on the lower applicator roll 2) can be adjusted.

Also, the paper-roll moving mechanism is used to properly move the paperroll 7 in the required direction so that the angle at which the web 1enters between the web-nipping portions 20 can be adjusted.

Since the coating apparatus of the second embodiment of the presentinvention is constructed as described above, the same advantages as thefirst embodiment can be obtained by applying a coating solution to theweb 1 with the coating apparatus. In addition, the position of the miniturn bar 4 is adjusted with the mini-turn-bar moving mechanism, wherebythe contact length that the web 1 that contacts one (lower) of the twoapplicators 2 can be adjusted. And the angle at which the web 1 entersbetween the web-nipping portions 20 is adjusted by adjusting theposition of the paper roll 7 with the paper-roll moving mechanism,whereby the contact length that the web 1 contacts the other (upper)applicator roll 2 can be adjusted. Thus, the separation condition of theweb 1 from one of the two applicator rolls 2 and coating conditions forboth sides of the web 1 can be freely adjusted.

(C) Third Embodiment

Now, a third embodiment of the present invention will be described inconjunction with the drawings.

FIG. 5 shows a simplified side view of a coating apparatus constructedin accordance with the third embodiment of the present invention. In thefigure, the same reference numerals as FIGS. 1 and 4 denote the sameparts and a description of these parts will be partly omitted.

As illustrated in FIG. 5, the coating apparatus of the third embodimenthas the same mini turn bar 4 as the second embodiment to the downstreamside of web-nipping portions 20. The coating apparatus further has thesame guide roll (paper roll) 7 as the second embodiment to the upstreamside of the web-nipping portions 20.

In the third embodiment, the mini turn bar 4 is arranged so that the web1 is wound around an upper applicator roll 2, and the paper roll 7 isarranged so that the web 1 is wound around a lower applicator roll 2.However, the mini turn bar 4 and paper roll 7 may be arranged in reverseorder with respect to the upper and lower applicator rolls 2,2.

In the third embodiment, a turn bar 5 and drier 6 are arranged to thedownstream side of the applicator rolls 2,2 in the recited order, aswith the first embodiment. However, they are arranged properly inaccordance with device-installation environment, etc.

And in the third embodiment, the same mini turn bar 4 and paper roll 7as those of the second embodiment are provided with moving mechanisms(not shown), respectively.

The paper-roll moving mechanism is the same as that of the secondembodiment. The mini-turn-bar moving mechanism is able to adjust thecontact length that the web 1 contacts one (upper) of the two applicatorrolls 2 (distance that the web 1 is held on one of the two applicatorrolls) by moving the mini turn bar 4 in the diameter direction of theapplicator roll 2. The mini-turn-bar moving mechanism is also able tomove the mini turn bar 4 from the web 1 to the position indicated byreference numeral 4′ in FIG. 4.

Since the coating apparatus of the third embodiment of the presentinvention is constructed as described above, the same advantages as thesecond embodiment can be obtained by applying a coating solution to theweb 1 with the coating apparatus. In addition, the mini turn bar 4 canbe moved away from the path of the web 1, so working space can beensured by moving the mini turn bar 4 away from the path of the web 1during paper travel or maintenance of equipment. Thus, the advantage ofenhancing operation efficiency is obtained.

The paper-roll moving mechanism may also be constructed so that it canmove the paper roll 7 away from the path of the web 1 to enhanceoperation efficiency.

In the case where there is a need for the web 1 to travel horizontallyfor reasons such as an enhancement in the operation efficiency of paperpassage, etc., there is an alteration such as the one shown in FIG. 6.Note that in the figure, the same reference numerals as FIGS. 1, 4, and5 denote the same parts.

In this case, as illustrated in FIG. 6, one of the two applicator rolls2 (e.g., an upper application roll in FIG. 6) is constructed so that itis movable in a direction away from and toward the web 1 (verticaldirection in FIG. 6) at a position where the center axis of the upperapplicator roll 2 is offset horizontally from the center axis of theother applicator roll 2 (e.g., a lower application roll in FIG. 6). Bymoving the upper applicator roll 2 from reference numeral 2′ toreference numeral 2 in an arrow-indicating direction and pressing theupper applicator roll 2 against the lower applicator roll 2, the web 1can be wound around the lower applicator roll 2.

To adjust the length that the web 1 is wound around the lower applicatorroll 2, there are provided a paper roll 7 and a paper-roll movingmechanism (not shown) to the side upstream of the applicator rolls 2.Also, there are provided an air-flotation type mini turn bar 4 and amini-turn-bar moving mechanism (not shown) to the downstream side of theapplicator rolls 2. Therefore, the paper roll 7 is movable fromreference numeral 7′ to reference numeral 7 (see a arrow) and the miniturn bar 4 is movable from reference numeral 4′ to reference numeral 4(see an arrow). The embodiment shown in FIG. 6 further includes adownstream paper roll (fixed position) 7, which is mounted between themini turn bar 4 and drier 6.

In the above-described case, a coating solution on the applicator roll 2is permeated into the web 1 while the web 1 is being held on theapplicator roll 2, and the fluidity and tack strength diminish.Therefore, even if the separation angle α of the web 1 from theapplicator roll 2 is small, the separation position of the web 1 fromthe applicator roll 2 becomes stable and the advantage of reducing thequantity of a mist is obtained.

Of course, the length that the web 1 is wound around one of the twoapplicator rolls 2 and the separation angle of the web 1 from theapplicator roll 2 can be altered by adjusting the position of theapplicator roll 2 and/or the position of the mini turn bar 4. Also, thelength that the web 1 is wound around the other applicator roll 2 can bealtered by adjusting the position of the upstream paper roll 7.

(D) Others

While the present invention has been described with reference to thepreferred embodiments thereof, the invention is not to be limited to thedetails given herein, but may be modified within the scope of theinvention claimed. For example, the structure of the mini turn bar(air-flotation type mini turn bar) used in the coating apparatus of thepresent invention is not limited to the structure shown in FIGS. 3A and3B. Preferred examples are the structures of mini turn bars 30A, 30B,30C, 30D, 30E, 30F, and 40 shown in FIGS. 7 to 13.

The mini turn bar 30A shown in FIG. 7 is a first preferred structureexample. This mini turn bar 30A is equipped with a box-shaped main body31 that has no cover. Compressed air from an air supply source (notshown) is supplied to the interior space 31 a of the bar main body 31.The upper portions of the side walls 31 b and 31 c of the bar main body31 diminish in width toward an opening, in which a U-shaped cover member32 is arranged with its opening downward. Between the upstream side wall31 b and the cover member 32, there is provided an upstream gap(slit-shaped groove). The upstream gap serves as the exit of a first airnozzle 35A that is formed by the side wall 31 b of the bar main body 31and the side wall 32 b of the cover member 32. Similarly, between thecover member 32 and the downstream side wall 31 c, there is provided adownstream gap (slit-shaped groove). The downstream gap serves as theexit of a second air nozzle 35B that is formed by the side wall 32 c ofthe cover member 32 and the side wall 31 c of the bar main body 31.

In close proximity to the exits of the air nozzles 35A and 35B,partition members 34A, 34B in the form of a round bar are provided onthe top surface 32 a of the cover member 32 and extend in the widthdirection of the web 1. Also, L-shaped plates 33A, 33B are attached tothe exterior surface of the side walls 31 b, 31 c of the bar main body31 and extend in the width direction of the web 1. With thisarrangement, between the air nozzles 35A and 35B there is formed astatic pressure pocket (first air pocket) 36A that is defined by thepartition members 34A, 34B and the top surface 32 a of the cover member32. Also, a static pressure pocket (second air pocket) 36B is formed tothe upstream side of the air nozzle 35A and is defined by the upstreamL-shaped plate 33A and the side wall 31 b of the bar main body 31.Further, a static pressure pocket (third air pocket) 36C is formed tothe downstream side of the air nozzle 35B and is defined by thedownstream L-shaped plate 33B and the side wall 31C of the bar main body31.

According to the mini turn bar 30A constructed as described above, theweb 1 can be stably supported by both the dynamic pressure of compressedair that is squired out of the first and second air nozzles 35A, 35B andthe static pressure of a layer of air within the first static pressurepocket 36A. Because the second and third static pressure pockets 36B,36C are also provided at the inlet portion and outlet portion of thearcuately curved portion of the web 1, the flap of the web 1 against themini turn bar 30A at the inlet and outlet portions can be suppressed bythe static pressure of the air layers within the second and third staticpressure pockets 36B, 36C. Thus, the web 1 can be prevented fromcontacting the mini turn bar 30A. As illustrated in FIG. 7, the shape ofthe mini turn bar 30A, which leads from the second static pressurepocket 36B on the inlet side to the third static pocket 36C on theoutlet side, is symmetrically formed with respect to a center line Lpassing through the center of the first static pressure pocket 36A.Therefore, the web 1 is able to travel in a fixed radius of curvatureand stable web travel becomes possible. Thus, according to the mini turnbar 30A, the web 1 is able to travel with a sufficient quantity offlotation and the problem of flaws in a coated surface due to contactcan also be prevented.

In experiments using the mini turn bar 30A, in the case where thepressure of compressed air is 2000 mmAq (19.6 kPa) in gage pressure andthe radius R of curvature of the web 1 is 160 mm, good results have beenobtained when the slit width t of the exits of the air nozzles 35A, 35Bis in a range of 0.5 to 5.0 mm and the diameter φ of the partitionmembers 34A, 34B in a range of 1 to 10 mm. The radius R of curvature ofthe web 1 is determined by the shape of the mini turn bar 30A, and asthe radius R of curvature becomes smaller, the reaction force that themini turn bar 30A undergoes from the web 1 through a layer of airbecomes greater. Since the mini turn bar 30A has along and narrowstructure extending in the width direction of the web 1, it ispreferable that the radius R of curvature be 100 mm or greater, ifrigidity is taken into consideration.

The mini turn bar 30B shown in FIG. 8 is a second preferred structureexample. This mini turn bar 30B is an alteration of the first mini turnbar 30A. The side walls 31 b, 31 c of the bar main body 31 of the secondmini turn bar 30B are partly different from the first mini turn bar 30A.That is, the upper portions of the side walls 31 b, 31 c of the bar mainbody 31, as with first example, diminish in width toward an opening, butthe upper ends are vertically formed and are parallel to the side walls32 b, 32 c of a cover member 32. With such a construction, the air-jetdirections of air nozzles 35A, 35B in the second example areapproximately parallel to a center line L, and as illustrated in FIG. 8,a second static pressure pocket 36B and third static pressure pocket 36Cat the inlet and outlet portions can be made deeper than the firstexample.

The mini turn bar 30C shown in FIG. 9 is a third preferred structureexample. While the first mini turn bar 30A forms the static pressurepocket 36A by installing the partition members 34A, 34B in the shape ofa bar on the top surface 32 a of the cover member 32, the mini turn bar30C of the third example is characterized in that a static pressurepocket 36A is formed by mounting a U-shaped plate 38 with left and rightside walls 38 b, 38 c on the top surface 32 a of a cover member 32. TheU-shaped plate 38 is formed from a thick member, and the upper roundcorners of the left and right side walls 38 b, 38 c has a radius r ofcurvature, as shown in FIG. 9.

The mini turn bar 30D shown in FIG. 10 is a fourth preferred structureexample. This mini turn bar 30D is an alteration of the third mini turnbar 30C, and the upper portions of the side walls 31 b, 31 c of a barmain body 31 are formed the same as the second example. In the third andfourth mini turn bars 30C and 30D, under the same conditions as thefirst example, good results have been obtained when the height d of theside walls 38 b, 38 c of the U-shaped plate 38 (pocket depth d) is 1 to20 mm, the difference h in height between the side walls 38 b, 38 c ofthe U-shaped plate 38 and the side walls 31 b, 31 c of the bar main body31 is −5 to 3 mm, and the radius r of curvature of the side walls 38 b,38 c of the U-shaped plate 38 is 0.5 to 5 mm. The upper ends of the sidewalls 38 b, 38 c of the U-shaped plate 38 may be chamfered instead ofbeing rounded.

The mini turn bar 30E shown in FIG. 11 is a fifth preferred structureexample. This mini turn bar 30E is an alteration of the fourth mini turnbar 30D, and within a static pressure pocket 36A, there is provided anair nozzle (third air nozzle) 39 from which compressed air is squirted.The air nozzle 39 has an opening in the top surface of a U-shaped plate38 and is connected to an air supply source (not shown). The air supplysource to which the third air nozzle 39 is connected may be the samesystem as an air supply source to which first and second air nozzles35A, 35B are connected, or a different system. Preferably, the airsupply system is constructed so that the third air nozzle 39 can squirtcompressed air higher in pressure than the first and second air nozzles35A, 35B.

The above-described mini turn bar 30E has the following advantages. Thatis, as the web 1 travels near the mini turn bar 30E, the air within thecentral static pressure pocket 36A passes over the side wall 38 c of theU-shaped plate 38 that is the partition wall portion between the staticpressure pockets 36A and 36C, and flows into the downstream staticpressure pocket 36C. At this partition wall portion the web 1 issupported by the pressure of the wake air, but the flow passage area ofthe wake air at that partition wall portion widens gradually from thecenter static-pressure pocket 36A toward the downstream static-pressurepocket 36C, as shown in FIG. 11. Therefore, the dynamic pressurecomponent of the wake air at the partition wall portion is graduallyreduced as the flow passage area enlarges. Because of a reduction in thedynamic pressure of the wake air, if the pressure of the wake airbecomes smaller than the tension of the web 1 or force of pushing theweb 1 toward the mini turn bar 30E such as atmospheric pressure, etc.,then the web 1 will contact the partition wall portion. However, in thismini turn bar 30E, the static pressure component of the wake air flowingout from the static-pressure pocket 36A is enhanced by compressed airsquirted from the air nozzle 39, so a compensation for a reduction inthe dynamic pressure can be made and contact between the web 1 and thepartition wall portion can be prevented.

The mini turn bar 30F shown in FIGS. 12A and 12B is a sixth preferredstructure example. This mini turn bar 30F is an alteration of the fourthmini turn bar 30D and is characterized in that there is provided alabyrinth structure in each of the static pressure pockets 36A, 36B, and36C. That is, as shown in FIGS. 12A and 12B, the static pressure pockets36A, 36B, and 36C are provided with a plurality of baffle plates(partition wall) 37A, 37B, and 37C, which are arranged at predeterminedintervals in the longitudinal direction of the mini turn bar 30F (widthdirection of the web 1). The baffle plates 37A, 37B, and 37C segmenteach of the static pressure pockets 36A, 36B, and 36C into a pluralityof sections.

According to the mini turn bar 30F, the baffle plates 37A, 37B, and 37Cgive strong resistance to air flowing between the web 1 and the miniturn bar 30F. That is, the baffle plates 37A, 37B, and 37C form a sortof labyrinth structure between the web 1 and the mini turn bar 30F. Thelabyrinth structure converts the kinetic energy of air into pressure, sothe static pressure within each of the static pressure pockets 36A, 36B,and 36C rises. Also, when the web 1 shifts laterally, there is apossibility that pressure will leak from gaps formed in the widthdirection of the web 1, but since each of the static pressure pockets36A, 36B, and 36C is segmented into a plurality of sections, afluctuation in web-supporting pressure due to the lateral shift of theweb 1 can be minimized. Therefore, the mini turn bar 30F is capable ofsupporting the web 1 more stably by such a labyrinth structure andpreventing the web 1 from vibrating and making a noise. In the mini turnbar 30F, while each of the static pressure pockets 36A, 36B, and 36C isprovided with a labyrinth structure, all the static pressure pockets36A, 36B, and 36C does not always need to have a labyrinth structure.For instance, even when only the center static pressure pocket 36A has alabyrinth structure, the above-described advantages are obtained.

The mini turn bar 40 shown in FIG. 13 is a seventh preferred structureexample. This mini turn bar 40 is equipped with a box-shaped main body41 having no cover, and compressed air from an air supply source (notshown) is supplied to the interior space 41 a of the bar main body 41.Within the opening of the bar main body 41, a U-shaped cover member 42is arranged with its opening downward. Between the side walls 41 b, 41 cof the bar main body 41 and the side walls 42 b, 42 c of the covermember 42, there are formed passages 45A, 45B, which are incommunication with the interior space 41 a. These passages 45A, 45Bserve as air nozzles that squirt compressed air out of the interiorspace 41 a. They will hereinafter be referred to as air nozzles.L-shaped flange members 48A, 48B are attached to the interior surface ofthe side walls 41 b, 41 c of the bar main body 41, and between the upperends of the flange members 48A, 48B and the lower ends of the side walls42 b, 42 c of the cover member 42, the inlet portions of the first andsecond air nozzles 45A, 45B into which compressed air flows from theinterior space 41 a are narrowed down.

U-shaped partition members 44A, 44B are arranged left and right on thetop surface 42 a of the cover member 42 with their openings downward.The lower ends of the inner side walls 44Ab, 44Bb of the partitionmembers 44A, 44B are mounted on the top surface 42 a of the cover member42, and between the lower ends of the outer side walls 44Ac, 44Bc andthe top surface 42 a of the cover member 42, there are formed gapsthrough which the interiors of the partition members 44A, 44Bcommunicate with the air nozzles 45A, 45B. The side walls 41 b, 41 c ofthe bar main body 41 extend near the top surfaces 44Aa, 44Ba of thepartition members 44A, 44B, and between the upper end portions of theside walls 41 b, 41 c of the bar main body 41 and the partition members44A, 44B, there are formed slit-shaped grooves 451B and 451C extendingin the width direction of the web 1. The top surfaces 44Aa, 44Ba of thepartition members 44A, 44B are formed into curved surfaces, whichcorrespond to the curved path of the web 1. The curved tope surfaces44Aa, 44Ba have a great number of bores 452 arranged evenly in zigzags.The grooves 451B, 451C and bores 452 form the exits of the air nozzles45A, 45B. The grooves 451B, 451C will hereinafter be referred to asair-jet grooves and the bores 452 will hereinafter be referred to asair-jet bores. Also, the top surfaces 44Aa, 44Ba of the partitionmembers 44A, 44B in which the air-jet bores 452 are formed willhereinafter be referred to as air-jet surfaces.

The above-described partition members 44A, 44B form a static pressurepocket (first air pocket) 46A along with the top surface 42 a of thecover member 42. Within the static pressure pocket 46A, there isarranged a reinforcement plate 47 through which both partition members44A and 44B are connected. Also, L-shaped plates 43A, 43B are attachedto the exterior surfaces of both side walls 41 b, 41 c of the bar mainbody 41 and extend in the width direction of the web 1. With thisconstruction, a static pressure pocket (second air pocket) 46B, which isdefined by the upstream L-shaped plate 43A and the side wall 41 b of thebar main bar 41, is formed to the downstream side of the air nozzle 45A.Similarly, a static pressure pocket (third air pocket) 46C, which isdefined by the downstream L-shaped plate 43B and the side wall 41C ofthe bar main bar 41, is formed to the upstream side of the air nozzle45B.

According to the mini turn bar 40 with such a construction, the web 1can be stably supported by both the dynamic pressure of the compressedair squired from the air nozzles 45A, 45B and the static pressure of thelayer of air within the static pressure pocket 46A formed on the topsurface 42 a of the cover member 42. In addition, in this mini turn bar40, the static pressure pockets 46B, 46C are provided at the inlet andoutlet portions of the curved portion of the web 1, so the flap of theweb 1 against the mini turn bar 40 at the inlet and outlet portions canbe suppressed by the static pressure of the air layers formed within thestatic pressure pockets 46B, 46C, and the contact of the web 1 with themini turn bar 40 can be prevented.

Also, as the web 1 travels near the mini turn bar 40, the air within thecentral static pressure pocket 46A passes over the partition member 44Bthat is the partition wall portion between the static pressure pockets46A and 46C, and flows into the downstream static pressure pocket 46C.At this partition wall portion the web 1 is supported by the pressure ofthe wake air, but the flow passage area of the wake air widens graduallyfrom that partition wall portion toward the downstream static-pressurepocket 46C. Therefore, the dynamic pressure component of the wake air atthe partition wall portion is gradually reduced as the flow passage areaenlarges. Because of a reduction in the dynamic pressure of the wakeair, if the pressure of the wake air becomes smaller than the tension ofthe web 1 or force of pushing the web 1 toward the mini turn bar 40 suchas atmospheric pressure, etc., then the web 1 will contact the bafflewall portion. However, in this mini turn bar 40, the top surface 44Ba ofthe partition member 44B that is the partition wall portion is used asthe air-jet surface, so contact between the web 1 and the partitionmember 44B can be prevented by a layer of compressed air that is squiredout of the air-jet surface 44Ba. Also, by forming the air-jet groove451B on the downstream side of the air-jet surface 44Ba, a curtain ofcompressed air from the air-jet groove 451B can prevent the air squirtedout of the air-jet surface 44Ba from leaking out as the web 1 travels,and a layer of air can be reliably formed between the web 1 andpartition member 44B.

Moreover, the shape of the mini turn bar 40, which leads from theupstream static pressure pocket 46B to the downstream static pocket 46C,is symmetrically formed with respect to a center line L passing throughthe center of the center static pressure pocket 46A, so the web 1 isable to travel in a fixed radius of curvature and stable travel of theweb 1 becomes possible.

According to these mini turn bars 30A, 30B, 30C, 30D, 30E, 30F, or 40,the web 1 is able to travel stably with a sufficient quantity offlotation without contacting the mini turn bar. Therefore, if a coatingsolution is applied to the web 1 by the coating apparatus equipped withthe mini turn bar 30A, 30B, 30C, 30D, 30E, 30F, or 40, the quality ofthe coated paper can be further enhanced.

Also, the respective characteristic constructions of the mini turn bars30A, 30B, 30C, 30D, 30E, 30F, and 40 can be combined together. Forinstance, the labyrinth structure of the six mini turn bar 30F can beprovided in the other mini turn bars 30A, 30B, 30C, 30D, 30E, and 40.The third air nozzle 39 of the fifth mini turn bar 30E can also beprovided in the other mini turn bars 30A, 30B, 30C, 30D, 30F, and 40.

1. An apparatus for transferring and applying a film of coating solutionon each of two applicator rolls to each side of a web as it passesbetween nipping portions of said two applicator rolls which are formedwhen they are pressed against each other, said apparatus comprising: anair-flotation type turn bar, provided to the downstream side of saidnipping portions, for conveying said web while holding said web on asurface of one of said two applicator rolls, after said web passesbetween said nipping portions.
 2. The apparatus as set forth in claim 1,further comprising: a mechanism for moving said turn bar.
 3. Theapparatus as set forth in claim 2, wherein said turn-bar movingmechanism is constructed to adjust a distance that said web is held onsaid one applicator roll.
 4. The apparatus as set forth in claim 2,wherein said turn-bar moving mechanism is constructed to adjust adistance between said one applicator roll and said turn bar.
 5. Theapparatus as set forth in claim 1, further comprising: a paper roll,provided to the upstream side of said nipping portions, for conveyingsaid web while holding said web on a surface of the other of said twoapplicator rolls, before said web passes between said nipping portions.6. The apparatus as set forth in claim 5, further comprising: amechanism for moving said paper roll.
 7. An air-flotation type turn barfor causing a web to travel so as to form an arcuately curved portionaround said bar by floating said web with air, comprising: a first airpocket arranged inside the arcuately curved portion of said web; asecond air pocket provided adjacent to said first air pocket andarranged near an entrance portion of said curved portion; a third airpocket provided adjacent to said first air pocket and arranged near anexit portion of said curved portion; a first air nozzle provided betweensaid first air pocket and said second air pocket for squirting airtoward said web; and a second air nozzle provided between said first airpocket and said third air pocket for squirting air toward said web. 8.The air-flotation type turn bar as set forth in claim 7, furthercomprising: a third air nozzle for squirting higher-pressure air thanatmospheric pressure into said first air pocket.
 9. The air-flotationtype turn bar as set forth in claim 7, further comprising: a pluralityof first baffle walls provided in the direction of the width of said webwithin said first air pocket so that said first air pocket is segmentedinto a plurality of sections.
 10. The air-flotation type turn bar as setforth in claim 9, further comprising: a plurality of second baffle wallsprovided in the direction of the width of said web within said secondair pocket so that said second air pocket is segmented into a pluralityof sections; and a plurality of third baffle walls provided in thedirection of the width of said web within said third air pocket so thatsaid third air pocket is segmented into a plurality of sections.
 11. Theair-flotation type turn bar as set forth in claim 7, wherein: saidsecond air nozzle comprises a second air-jet surface and a secondslit-shaped air-jet groove, provided on a third surface extending in thedirection of the width of said web; said second air-jet surface has agreat number of air-jet bores and is provided near said first airpocket; and said second air-jet groove extends in the direction of thewidth of said web and is provided near said third air pocket.
 12. Theair-flotation type mini turn bar as set forth in claim 11, wherein: saidfirst air nozzle comprises a first air-jet surface and a firstslit-shaped air-jet groove, provided on said third surface extending inthe direction of the width of said web; said first air-jet surface has agreat number of air-jet bores and is provided near said first airpocket; and said first air-jet groove extends in the direction of thewidth of said web and is provided near said second air pocket.
 13. Theair-flotation type mini turn bar as set forth in claim 7, wherein ashape from said second air pocket to said third air pocket is formedsymmetrically with respect to a center line of said first air pocket.14. An apparatus for transferring and applying a film of coatingsolution on each of two applicator rolls to each side of a web as itpasses between nipping portions of said two applicator rolls which areformed when they are pressed against each other, said apparatuscomprising: the air-flotation type turn bar as set forth in claim 7,provided to the downstream side of said nipping portions for conveyingsaid web while holding said web on a surface of one of said twoapplicator rolls after said web passes between said nipping portions, byair squirted from said bar.
 15. A method of transferring and applying afilm of coating solution for coated paper production on each of twoapplicator rolls to each side of a web as it passes between nippingportions of said two applicator rolls which are formed when they arepressed against each other, said method comprising the step of:conveying said web while holding said web on a surface of one of saidtwo applicator rolls after said web passes between said nippingportions, by an air-flotation type turn bar.